1. Field of the Invention
The invention relates generally to superhydrophobic films and methods of making superhydrophobic films, and more specifically to superhydrophobic films having structured features formed from immiscible or phase-separated components.
2. Description of the Related Art
Traditional superhydrophobic coatings are soft in nature and have a surface chemistry that results in reduced adhesion and durability. Hence such coatings are often not suitable for robust applications, requiring surface hardness, durability, and adhesion. While there have been reports of superhydrophobic coatings in the literature, these films are mostly based on fabrication via methods of polymer reconformation, sol-gel, spray-on powder coatings, or self-assembly of nano-arrays or nano-structures onto surfaces. The polymer-based films are typically poorly bounded to the substrate, and thus are not sufficiently durable to satisfy most application requirements. Harsh chemical treatment procedures (i.e., use of chemical solvent mixtures) tend to degrade the physical properties of the underlying materials. Moreover, in many cases the toxicity of the different reagents used during the fabrication processes poses risk to human health and environmental concerns, which to date has limited these methods to laboratory research, and are unsuitable for commercial applications. Similarly, powder-based coatings also exhibit weak durability, because it is often necessary to use application-specific binding agents. On the other hand, while sol-gel based coatings have a propensity for better bonding, they generally exhibit poor hydrophobic qualities, i.e., a low water contact angle, due to a lack of nano-scale sharpening and porosity. Coatings based on nanoarrays or nanoparticles possess similar problems as in the case of polymer or sol-gel based films, in addition to exhibiting poor homogeneity. Furthermore, fabrication of these nanostructure assemblies involves elaborate processing schemes that can render them unsuitable for large-scale development and production.